Formation of l-alanine as a reduced end product in carbohydrate fermentation by the hyperthermophilic archaeon Pyrococcus furiosus |
| |
Authors: | Servé W. M. Kengen Alfons J. M. Stams |
| |
Affiliation: | (1) Department of Microbiology, Wageningen Agricultural University, Hesselink van Suchtelenweg 4, 6703 CT Wageningen, The Netherlands |
| |
Abstract: | The hyperthermophilic archaeon Pyrococcus furiosus was found to form substantial amounts of l-alanine during batch growth on either cellobiose, maltose or pyruvate. Acetate, CO2 and H2 were produced next to alanine. The carbon- and electron balances were complete for all three substrates. Under standard growth conditions (N2/CO2 atmosphere) an alanine/acetate ratio of about 0.3 was found for either substrate. The alanine /acetate ratio was influenced, however, by the hydrogen partial pressure. In the presence of S0 or in coculture with Methanococcus jannaschii this ratio was only 0.07, whereas under a H2/CO2 atmosphere this ratio could amount up to 0.8. Alanine formation was also aflected by the NHinf4sup+concentration, i.e. below 4 mM, NHinf4sup+becomes limiting to alanine formation. Alanine formation was shown to occur via an alanine aminotransferase, which exhibited a specific activity in cell-free extract of up to 6.0 U/mg (90°C; direction of pyruvate formation). The alanine aminotransferase probably cooperates with glutamate dehydrogenase (up to 23 U/mg; 90°C) and ferredoxin: NADP+ oxidoreductase (up to 0.7 U/mg, using methyl viologen; 90°C) to recycle the electron acceptors involved in catabolism. Thus, the existence of this unusual alanine-forming branch enables P. furiosus to adjust its fermentation, depending on the redox potential of the terminal electron acceptor.Abbreviations DTT dithiothreitol - MV methyl viologen - AAT alanine aminotransferase - GDH glutamate dehydrogenase - MV: NADP+ OR methyl viologen: NADP+ oxidoreductase |
| |
Keywords: | Pyrococcus furiosus Hyperthermophile Archaea Fermentation font-variant:small-caps" >l-alanine Alanine aminotransferase Glutamate dehydrogenase Interspecies hydrogen transfer |
本文献已被 SpringerLink 等数据库收录! |
|